Polyaryl-sulphones are a known class of thermoplastics and can be used in many ways (see, for example, Society of Plastics Engineers, 33rd Annual Technical Conference, May 5-8, 1975, pages 621 to 623).
The use of polyaryl-sulphones for certain industrial applications is restricted or even prevented by the embrittlement of the polyaryl-sulphones under load and the susceptibility of the polyaryl-sulphones to stress-cracking under the influence of solvents and under the action of solutions of unsaturated polyester resins.
It is proposed in DT-OS (German Published Specification) No. 1,719,244 and in U.S. Pat. No. 3,365,517 to reduce the undesired embrittlement of polysulphones under load by adding polymers, for example polycarbonates.
According to DT-OS (German Published Specification) No. 2,305,413 and U.S. Pat. No. 3,960,815, the susceptibility of polyaryl-ether-sulphones to stress-cracking is improved by branching of the polymer chain.